Now available via Software Update:
Security Update 2005-007 delivers a number of security enhancements and is recommended for all Macintosh users. This update includes the following components:
AppKit
BlueTooth
CoreFoundation
cups
Directory Services
HIToolBox
Kerberos
loginwindow
Mail
OpenSSL
QuartzComposerScreenSaver
Security Interface
Safari
X11
zlib
For detailed information on this Update, please visit this website: http://www.info.apple.com/kbnum/n61798
[Update] Apparently this update breaks the ability to process 64 bit application data. According to AppleInsider, Wolfram Research sent an email to customers suggesting they wait to install the update due to an error on Apple's part, and offers a workaround to turn off the 64 bit processing abilities in Mathematica to allow the app to run if the security patch had already been installed.